The present invention relates to a deformable heating element, particularly for heating the steering wheel of a motor vehicle.
To heat steering wheels, heating elements are needed that fit the cross-sectional shape of the steering wheel rim. Known heating elements for steering wheels consist of a flat base material that comprises metallic heating conductors on one side thereof. Steering wheel heaters are also known wherein the heating elements are embedded into foam material or into a thermoplastic. Heating elements made of textile layers and/or foam materials between which the heating conductor is inserted are also known.
DE 296 16 918 U1 describes a steering wheel with an integrated steering wheel heater. In this steering wheel heater the heating conductor is fused into a thermoplastic material. The fusion process takes place after a voltage has been applied to the heating conductor. In this process the heating conductor penetrates into the thermoplastic material to such an extent that the heating conductor is flush with the thermoplastic on the outside. With this embodiment of the heating conductor in the thermoplastic material, the heating wire does not become apparent or emerge on the outside of the outer cover and can also not be sensed or felt while the steering wheel is held.
EP 0 832 806 A1 describes a steering wheel with an integrated steering wheel heater. The steering wheel rim of the steering wheel is provided under its outer cover with a layer of thermoplastic material into which the heating wire is fused. In this embodiment, the heating wire can be flush with the layer of thermoplastic material on the outside or it can be fully coated with thermoplastic material.
DE 10 2006 004 145 A1 refers to an electric heating element. The heating element comprises a support, which may be made from any desired material, e.g. a textile fabric, a nonwoven, a film, a woven fabric, a knitted fabric, formed from synthetic or natural fiber material. The support is provided at least locally with an at least temporarily adhesive material exhibiting adhesiveness that can be activated in a selective way. The heating conductor is sewn to the support.
The above-mentioned heaters, in which the heating conductor is heated for manufacturing reasons to either activate an adhesive or to fuse the adhesive into a foam body, have the drawback that the heating conductors are already stressed to a very great degree during manufacture due to the heating to very high temperatures within a very short period of time so as to activate the materials and to be able to carry out the manufacturing process within very short cycle times. Furthermore, it may happen that the heating conductor becomes apparent or can be seen on the steering wheel cover.